Hi, would like some help. I replaced one of the boom cylinders and during the start up and bleeding I lost all power to the backhoe. The loader and stabilizers work just fine, plenty of power. When any of the cylinders are operated they move maybe 1/2" in and out thats it. The system is full of oil, the hoses are correct(though if behaves like there crossed?), I have removed and cleaned both high and low regen valves. I don't understand how the stabilizers work while hoe doesn't. I have read on here about bad quick connect o rings, and a power beyond valve, but wouldn't that effect the stabilizers too? Lost need help please.
I think you ought to check your hoses because they definitely sound crossed. In other words, if the hoses from the boom extend are crossed to the dipper extend (and vise versa) they could "jam" up in the valve. The reason being is that when the boom is trying to extend, the fluid on the other side of the cylinder is being trapped by the valve on the dipper section. So you are simply building up pressure on both sides of the cylinder and it won't move. I assume that you could hear the engine develop load and likely the fluid go over relief? I have a loader on my 4020 John Deere. Just the other day I connected the hoses to the wrong connectors and nothing would move except for about a half inch like you say. After I followed the hoses back to the control valve, sure enough I had two in the correct spots and two were backwards. Easy for me though since they are all quick disconnect fittings and I just swapped them around and I was back up and going. I have also had something very similar happen to my skidder. The return line had gotten plugged in one of the spool valves and it was causing the differential in pressure between inlet and outlet to get very small. I had no power to lift, but but could still move the boom if there werent logs in it. The only difference there is that ALL of the hydraulics were weak, not just a few functions. I ended up getting so torqued off I started to jam levers back and forth and all of a sudden it cleared out.
The hoses are correct, I only replaced the one boom cylinder and the hoses are straight forward. What else is allowing the system not build pressure. The engine doesn't even come close to bogging when any backhoe lever is used or all levers are actuated at once. somehow it is bypassing.
Stupid question, but are you sure you removed the protective caps / inserts from the new hose ends before you installed the hose? Did you stuff a rag or something into the port after you had taken the hose off initially to keep oil from leaking out? I hope you don't get offended that I am bringing this up, thinking you are an inept nincompoop or something of that sort. I only bring it up because I have seen it happen before where one of the caps works its way into the valve block sticking one of them open and allowing fluid to bypass. Will the boom go down at all under its own weight?
I can't tell you about the power beyond valve, you'll have to wait for the experts to stop in. My only thought is did you give it enough time to run all of the air out of the cylinder? If the cylinder is empty, it will take a minute to fill with fluid. If you cycle the valve one way for a few seconds, then the other way, the air is just cushioning the fluid flow, and the cylinder won't move.
During the time I was trying to bleed the system initially, the boom would not move up or down so I operated the other levers and all of a sudden the boom and every thing dropped and the system will not hold pressure. I then continued to run the tractor at all rpms trying to get the air out for at least 30 min's with no luck. I have also let it sit for a couple days cleaned the regen valves(no crud found) then run it , still no go. Any more thoughts?
Something is wrong in your valve block. Perhaps one of the seals went out, a piece of debris is in there that you don't know about, or your relief valve has a piece of crud lodged in it keeping it open and bypassing the spools. That is about the only thing I can think of if the hoses are correctly hooked up.
I 'm going to check the relief valves next ,starting with the dipper because it will not move at all, thanks for your help.
No problem. Keep us posted, I would be curious to see what you find. Having dealt with hydraulic issues for years now (including designing hydraulic systems) they always intrigue me. Take this machine for instance: A buddy of mine did all of the hosing on it. There were over 300 miles of hydraulic hose in this machine.
The manual shows pressure to BHCV via a power beyond fitting at the stabilizer CV. The parts manual does not show a power beyond fitting that I can see. Certainly worth a look there. Would explain the stabilizers working & not the hoe....
Well the relief's all looked fine,I haven't had a chance to see if there is a power beyond valve off the stabilizers yet. Question, if one of the control valves check valves was stuck open would that bleed fluid from all the valves or just the on its on. still learning?
I suppose it could... Thinking of mine, if I am giving full boom flow, nothing else moves until I back off on the boom and then I can move multiple sections... I guess I have gotten so proficient at running her, I would need to fire my machine up and play with it to try certain things... Can't now though... I am vexed!
Same here on my 580CK, have to balance the pressures manually. A whole nother world from the new variable pump parallel circuit machines.
GOT IT!!!! Started at the beginning, removed the inlet regeneration valve again, and found a small piece of crap lodged in the poppet. Time to put her back to work. Thanks All for your help!!
Awesome! It is always something stupid like that, that always screws something up.